This invention relates generally to wireline and wireless telephone networks and is particularly directed to the handoff of calls from a wireless network to a wireline network either manually under the control of a subscriber or automatically such as in the event of a weak received signal.
Telephone-communication today is accomplished either by a wireline or a wireless telephone network. The wireline telephone network includes a first voice terminal (first subscriber set), a wireline to a switching office, large capacity physical trunks between switching offices, and a wire line to another voice terminal, (second subscriber set). The switching offices as well as the connection between the switching offices is known as a Public Switched Telephone Network (PSTN). The major components of a wireless telephone network, or cellular system, include a Mobile Switch Center (MSC), a Base Station (BS), also known as a Cell Site (CS), and a Mobile Station (MS), also known as a Mobile Unit (MU). The MSC interconnects the cellular system with the PSTN.
Currently, if a subscriber or user (which terms are used interchangeably hereafter) originates a telephone call on a cellular network and desires to continue the call on a wireline network the call must be disconnected on the cellular network and re-established on the wireline network. This is typically accomplished by terminating operation of the mobile unit, followed by initiating a new call via a wireline terminal to the directory number to which the terminated call was placed. Terminating the call on the cellular network and re-establishing the call on the wireline network may be desirable for various reasons. For example, the caller may wish to terminate the call on the cellular network and re-establish it on the wireline network to obtain the benefit of better voice quality and less expensive service on the wireline network. While it may be desirable under certain circumstances to transfer the call, the process of transferring the call is cumbersome, inefficient and time consuming.
In addition, today wireless users have available a call forwarding feature which may be used to temporarily direct inbound calls to another number which may be a wireline terminal number. Wireless calls may be forwarded to a wireline terminal to avoid wireless airtime charges or the effect of a low signal strength area when the mobile subscriber is near a designated wireline terminal. The process of activating/deactivating call forwarding is manual, cumbersome, and prone to error. Each time the wireless subscriber nears a wireline terminal to which it is desired to direct new, inbound calls, the subscriber must program the wireline terminal""s directory number as the forwarded number. Additionally, when the subscriber leaves the vicinity of the wireline terminal, the subscriber must deactivate call forwarding or inbound calls will continue to be sent to the wireline terminal that the subscriber is no longer in close proximity to.
The present invention addresses the aforementioned limitations of the prior art by providing for the handoff of a telephone call from a first wireless network to a second wireline network either manually or automatically. The present invention also provides for the automatic activation/deactivation of call forwarding to selected, preprogrammed wireline terminal numbers.
The present invention contemplates the handing off of telephone calls from a wireless network to a traditional wireline network either automatically or under the control of the subscriber. In order to later transfer a telephone call from the wireless to the wireline network, the subscriber, when in the vicinity of a designated wireline terminal to which it is desired to transfer a call, selects a transfer handoff key on the mobile terminal and enters the directory number (DN) of the designated wireline terminal. At this time, the wireless terminal determines the present coordinates of the subscriber by means of a satellite-based global positioning system (GPS) and stores the wireline terminal DN and present coordinates in a table in its memory for later use. The telephone number of the designated wireline terminal is thus matched with a given set of coordinates for possible future use in transferring a wireless telephone call to the wireline network.
When the subscriber desires to transfer a wireless call to the wireline network, the subscriber selects the handoff function key on the mobile terminal. The mobile terminal then determines its present coordinates using GPS information, compares its present coordinates with the coordinates of various wireline terminals whose directory numbers are stored in memory, determines the wireline terminal closest to its present coordinates within a predetermined range from its present coordinates, and transfers the call to that wireline terminal. Transfer of the call from the wireless network to the wireline network is accomplished by the wireless terminal providing the wireline directory number of the designated wireline terminal to the Mobile Switching Center (MSC) of the wireless network. The MSC then bridges the wireless call to the wireline terminal and provides a signal to the designated wireline terminal. The subscriber then picks up the receiver at the designated wireline terminal resulting in an xe2x80x9canswerxe2x80x9d signal being transmitted from the designated wireline terminal to the MSC. The MSC then drops the connection to the wireless terminal while maintaining the connection between the designated wireline terminal and the other party.
Another embodiment of the invention allows a subscriber to have wireless calls automatically forwarded to a designated wireline terminal (or perhaps plural wireline terminals) if the signal strength is weak whenever the wireless terminal is within a predetermined distance from the wireline terminal (or terminals) as determined by the location of both terminals using GPS coordinate information. This allows for the automatic forwarding of a wireless telephone call to the nearest wireline terminal to provide the best possible telephone call reception.